The invention relates to a modeling device for manually applying and modeling substances, namely wax, which are flowable when subjected to heat.
Modeling devices are known per se in connection with various functions, in particular for various materials. One important application area relates to prosthodontics, in particular the application of wax to the crown region of a tooth to be modeled. It is known on the one hand such that by means of a modeling tip wax is received in a flowable consistency, i.e. it can be modeled in a plastic manner, and transferred to the crown region, where it is subsequently worked. As the spatial structures to be worked are relatively small, this activity requires that the wax to be applied is metered in an extremely precise manner. Also, it is laborious and time-consuming using a modeling tip for the flowable wax to be received and applied at a site which is remote from the processing location.
A modeling device is known from Dental-Labor XLVIII, Issue 4/2000, wherein a tank which receives a wax cartridge is provided within a modeling device and said tank can be heated electrically to the same extent as a modeling tip. A mechanical push button is used to meter the wax which issues out of the modeling tip and the modeling device is operatively connected to an energy supply unit.
A device for wax modeling cast models in dentistry is known from German Patent DE 94 12 336 U1, which device consists of an elongated, base body which is a similar shape to a writing device and which serves as a storage chamber for the wax and whose funnel-shaped end region is provided with an outlet orifice and a coupling part, onto which coupling part conventional modeling tips can be placed. The wax storage chamber is encompassed by electrically heatable heating elements in the form of a heating mat which is connected to a thermostat, adjusting elements and a display device. Once the entire wax storage chamber has been heated, a heat insulation layer is provided between the casing of the base body and the heating mat. The end region, remote from the modeling tip, of the base body serves to insert wax cartridges known per se into the wax storage chamber, wherein likewise a pneumatically operated piston-cylinder unit is inserted via this end region into the base body and forms a forward-feed drive. For control purposes, the device is provided with sensor buttons which are located on the front side end of the base body facing the modeling tip. Depending upon the temperature of the melted wax inside the wax storage chamber, it can be difficult to meter in a precise manner the wax to be dispersed. It is a drawback as far as the operating technology is concerned, that the end remote from the modeling tip is not only connected to lines for supplying compressed air but is also connected to lines for supply electrical energy. This not only impairs the view of the immediate working region of the modeling tip but precise movements are also difficult. A further unfavorable condition is the complete encasement of the wax storage chamber in a heat-insulating material, as this inevitably leads to an increase in the cross-sectional dimensions of the device.
A further comparable device is known from German Patent DE 33 46 254 A1, which device consists of an elongated base body, wherein the wax cartridges to be processed can be inserted either via the rear side end of the base body or via the front side end thereof, in other words, in each case having first dismantled the function elements located on these two ends. However, as a departure from the subject matter of the aforementioned DE 94 12 336 U1, only the frontal side end is heated, i.e. the end facing the modeling tip, so that there is no necessity to encase the wax storage chamber in a heat-insulating casing. The forward-feed drive used can comprise an electromotor or also a piston cylinder unit requiring a supply of compressed air. However, a disadvantage of this known device is also the condition that connection lines for supplying electrical energy and optionally also for supplying the compressed air are located on the rearside end, i.e. the end remote from the modeling tip. Finally, it is comparatively complicated to use a wax cartridge which is to be processed.
It follows from this that the object of the invention is to provide a modeling device in accordance with the generic type such that in addition to facilitating the handling of the modeling device, the metering of the substance to be applied and the application procedure as such are also facilitated. This object is achieved in the case of such a device by virtue of a stylus having a chamber and a closable opening therein for inserting a wax cartridge into the chamber, a piston being positioned within the chamber and connected to a spindle nut and a threaded spindle, the piston forming the force-transmitting member between the threaded spindle and the modeling substance, a cable from an energy supply being attached to a front region of the stylus facing a modeling tip positioned on the front region.
In a manner known per se, a motorized forward-feed drive for the substance to be processed is located inside the modeling device and the intended purpose of the said drive is to move this substance for processing in the direction towards the modeling tip. Morever, a heating device is provided, which is capable of heating the substance substantially only at the end of the device facing the modeling tip and in particular until it issues out of the outlet of the modeling tip. In other words, it is not the intention to heat the substance completely to render it all into a liquid state, which in addition to other disadvantages would not only be associated with a certain expenditure of time but would simultaneously also be associated with a corresponding expenditure of energy. Thus, only that region of the substance is heated which during the procedure of being applied to the crown region to be modeled, namely when exiting out of the said outlet, is subjected to plastic deformation and accordingly must be sufficiently flowable. Finally, a switching device is provided, which is connected directly to the modeling device and during the working procedure is subjected to the immediate influence of the user of the modeling device. This switching device serves to control both the forward feed drive and also the heating device. It is preferably provided that the forward feed rate can be continuously regulated within a fixed feed rate range which is tailored to suit the working process. The same applies for the heating device. In particular, the heat which is to be imparted into the substance being processed can preferably be regulated likewise within a fixed range. The user of the modeling device thus has the opportunity to control both the forward feed and also the consistency of the substance being processed in a manner tailored to suit the working step and also the characteristics of the substance.
In accordance with the invention, the base body of the modeling device or stylus is provided with an orifice which is intended for introducing the substance which is a solid body in its initial state. This orifice can be closed and any flap or closing mechanism which does not impair the handling of the modeling device may be used for this purpose.
The components of the forward feed drive in accordance with the invention are formed by an electromotor, a threaded spindle and a spindle nut, wherein for example the threaded spindle is mounted in a non-rotatable manner within the modeling device, so that a rotation of the spindle nut can generate a forward feed movement in the longitudinal direction of the modeling device. The rotational speed of the motor and the pitch of the threaded spindle are designed with respect to the control range of the forward feed rate. A piston which is connected to the threaded spindle serves to provide a large-surface force-transmitting element which is directly connected to the substance which is to be processed. Both for reasons of weight and also to avoid the view being impaired, the cable is preferably attached to the front side end of the modeling device, i.e. the end of the modeling device facing the modeling tip, and extendsxe2x80x94in the direction towards the front sidexe2x80x94at an acute angle with respect to the longitudinal axis of the modeling device. This embodiment also serves to simplify the practical handling and thus ensures a working result of high quality.
The heating device can be formed by a coil arrangement which serves to heat that part of the substance being processed which is facing the front side region, i.e. the region adjacent to the modeling tip. In a particularly advantageous manner it is possible to provide several coils which are independent of each other and whose heating capacities can be controlled independently of each other. In this manner one coil can serve to provide basic heating and a further coil is designed merely for providing power peaks. The coils can be controlled, as far as their heating capacity is concerned, independently of each other. However, it is also possible to use in place of the coil arrangements any other flat surface heat conductor structures which heat up as a result of a current passing through them and which are designed to transmit heat to the substance which is being processed.
The molding tip comprises an end section which is bent at an angle with respect to the longitudinal axis of the modeling device. An alternative arrangement could also be a corresponding curvature. This embodiment improves the line of view of the respective user to the site where the substance is currently being applied. The same applies for the site where a modeling procedure is being performed using the modeling tip. This embodiment thus improves the working opportunities in the chewing surface depth.
The switching elements of said device are formed by sensors which render it possible to perform switching procedures without jarring so that neither the application procedure nor the metering and modeling procedure are impaired by these switching procedures. The extent to which the heating and to the same extent the forward feed movement can be controlled is selected in dependence upon the characteristics of the substance which is to be processed.
The modeling or dispensing tip of the modeling device can in addition be heated in a controlled manner. In this way, the forward feed and the procedure of metering the substance which is to be processed can be further improved.
The modeling device can be provided with an end switch which then triggers the automatic return of the forward feed drive to its initial position when the substance which is to be processed has been dispensed from the modeling device.
In the forward feed drive, a spindle nut is fixed, i.e. it is disposed within the elongated base body or stylus of the modeling device in such a manner as not to displace axially or rotate and a threaded spindle is provided which at one end is connected to the piston which is intended for forward feeding the wax cartridge which is to be processed and at its opposite end is connected to the motor. Both the piston and also the motor are arranged within the stylus in a non-rotatable manner, so that a rotational movement on the threaded spindle creates a corresponding axial displacement of the entire assembly consisting of the threaded spindle, motor and piston. The spindle nut fixedly arranged within the casing is located on the end of the stylus remote from the modeling tip, in particular the said cut-out.
The spindle nut can be designed fundamentally merely in the shape of a half-shell, so that a threaded engagement with the thread of the spindle shaft is only over a periphery of 180xc2x0. It has been established that such a limited threaded engagement can be regarded fundamentally as sufficient for the purposes of the subject of the invention. Furthermore, the spindle nut can also be formed as a longitudinally-divided body which consists of two half-shells which in their entirety can be completed to form a full cylindrical shell. Both variants offer fundamentally simple opportunities of releasing the threaded engagement between the spindle nut and the threaded spindle so that in the released state the entire assembly consisting of the piston, the threaded spindle and the motor can be displaced manually within the casing. Such a utilization is available when the casing in accordance with the invention is provided with a lateral cut-out through which the wax cartridge can be inserted. In this manner, the opportunity is available once the wax cartridge has been consumed for the piston to be displayed by manual intervention via the said cut-out back into its rearward position, i.e. the position which is suitable for inserting a new wax cartridge.
In the longitudinally-divided spindle nut, the two half-shells are accommodated in a bearing ring of elastomer material inside the stylus of the modeling device and moreover there are provided in a diametrically opposed position separating bodies which preferably comprise a wedge shape and which can be pressed in radially with respect to the likewise longitudinally-divided bearing ring in the gap between the two annular half-shells of the bearing ring, so that according to this movement a force can be exerted on the half-shells of the spindle nut, which force separates the said half-shells perpendicularly to their joint face. As a result of being received in the elastomer bearing ring, such a movement is likewise possible as the bearing ring deforms in an elastic manner and for this purpose it is designed accordingly in its dimensions and material. At the same time, in this manner the bearing ring serves to provide the necessary restoring force or it at least provides a contribution thereto. Moreover, it is advantageous to the invention that for the purpose of actuating the separating bodies an already existing sliding sleeve is involved. For example, the separating bodies can protrude slightly out of the outer surface of the modeling device, so that as a result of their xe2x80x9cextendingxe2x80x9d on the outerside they can be pressed inwards radially by means of the sliding sleeve. Likewise in the embodiment of this principle it can be provided that the wedge surfaces of the two separating bodies are connected to the bearing ring, for example adhered or vulcanized thereto and that as a result of extending over the radial outer sections of the separating wedges the material is displaced in a radially inwards direction and the bearing ring halves are removed from each other. When the bearing rings are in a state separated from each other in which the threaded engagement between the threaded spindle and the spindle nut is released, the separating bodies are thus elastically deformed, so that in turn restoring forces can be derived from this deformation state, which forces are released once the sliding sleeve has been removed and the bearing rings draw together, so that in turn a threaded engagement is produced between the spindle nut and the threaded spindle.
When the half-shells of the spindle nut are lying adjacent to each other their position is fixed in a from-locking manner relative to each other. This can be effected, for example, by means of engaging arrangements which are formed according to a type of tongue and groove connections, wherein a guiding effect can be exerted simultaneously on the half-shells by means of a conical design of the tongue and groove connections.
The drive principle mentioned in the first instance, where the spindle nut is only formed by one half-shell can be achieved in that the half-shell forms the closure of the cut-out in the wall of the casing of the modeling device, which cut-out is otherwise used to insert a wax cartridge. This means that the innerside of the half-shell is integrally provided with a threaded profile which extends over the peripheral angle of preferably 180xc2x0. This also means that the threaded engagement between this spindle nut and the threaded spindle can be released in an extraordinarily convenient manner, in that the said cut-out is merely revealed by removing the half-shell.
The modeling device is provided with a display device by means of which the user of the device is made aware of the extent to which the wax cartridge inserted has already been consumed, so that it might now be necessary imminently to insert a new wax cartridge. This is achieved by virtue of the fact that the displaced position of the piston, of the motor or any other function element which is connected to this assembly which can be displaced in the longitudinal direction of the device is visibly displayed towards the outerside of the device. By way of example only, this can be achieved by means of a signal body which is integrally formed on the motor casing, wherein this signal body is accommodated in a sliding manner in an outer cut-out of the casing.
A spring provides the opportunity of holding the wax cartridge constantly in a defined position relative to the piston within the casing of the device. Thus, the wax cartridge can be fed forward at any time in a manner free of play. This condition has a favorable effect with respect to metering in a precise manner the wax which is to be dispensed. As a result of the wax cartridge being in a defined position within the casing, reproducible heating conditions can be created to the same extent, a condition which is of importance for the rapid readiness for service of the modeling device.
Owing to the fact that it is not possible to exclude reliably impurities from the substance in the wax cartridge but also owing to the extraordinarily small dimension of the through-flow cross-section of the modeling tip, it is always to be expected that these cross-sections will become blocked. However, owing to these small dimensions cleaning to free this cross-section of blockages is time-consuming. To avoid these problems a sieve or filter is provided which has a mesh or pore width which is designed with respect to retaining offending foreign bodies. This sieve is provided within the stylus in such a manner that it can be replaced, a characteristic which can be advantageously achieved by means of an insertion piece which is releasably connected to the innerside structures of the device. This connection can be by way of a screw connection, a bayonet closure or the like. The sieve is thus changed merely by handling the substantially larger insertion piece.
The quantity of liquid substance issuing from the modeling tip should be tailored as precisely as possible to suit the actual requirements with respect to working accuracy. However, owing to the liquid wax portions located within the modeling tip and within the part chambers adjacent thereto within the casing of the modeling device, switching off the forward feed is associated with an unavoidable after-flow of wax and in fact in dependence on the consistency of the temperature of the wax and the pressure conditions prevailing in the said part chambers. In order to prevent this problem, a switching valve is provided, which switching valve is located in an expedient manner at the outlet of the casing and in fact immediately up stream of the entry cross-section of the modeling tip. In preference, an electromagnetic switching valve is used for this purpose, which valve is controlled by the user by means of a sensor which is attached to the front side, i.e. to the side facing the modeling tip. When this valve is closed, any further liquid wax portions are prevented from flowing out of the through-flow channel of the modeling tip owing to the vacuum created as a result of closing the valve and owing to the capillary effect also exerted owing to the small cross-section dimensions. It is possible to trigger a closure of this valve automatically and this closure can be associated, as far as switching is concerned, with a termination of the forward feed.
A consequence of switching off the forward feed movement is initially characterized by the pressure conditions being maintained within the device, which resultsxe2x80x94as mentioned abovexe2x80x94in a tendency for further substance to flow out of the modeling tip. This tendency is at least greatly reduced by virtue of the fact that the energy supply unit which also serves to control the forward feed is designed with the stipulation that once the forward feed procedure is completed, the piston is drawn back by a defined linear element, i.e. in the direction away from the modeling tip. This feature thus serves the comfort factor during the practical handling of the device and can likewise be automatically triggered according to predetermined linear elements. The linear elements are to be selected such that the spring mentioned in the introduction maintains its influence regardless of the piston having been drawn back.
Preferably the energy supply comprises an electric battery or can comprise an accumulator. The device in accordance with the invention can thus be operated independently from the mains.
The modeling tip is connected to the modeling device in such a manner that it can be replaced, so that if necessary in dependence upon the modeling procedures to be performed different modeling tips can be used. A triangular cross-sectional design of the elongated modeling device which in principle is similar to a writing device or stylus serves to improve the handling comfort.
The main area of application of the modeling device is the working procedure of applying wax in prosthodontics. The above described design principle can, however, be used in numerous other applications, where masses which are solid in their initial state, for example synthetic material, are applied in metered quantities to workpieces and must be modeled in a still flowing state. Finally one possible fundamental application is also during soldering procedures.